Rocket propellant



2,942,961 ROCKET PROPELLANT James R. Eiszner, Park Forest; m, and William G. Stanley, Hammond, Ind., assignorsfto Standard Oil Compan Chicago, a corporation of Indiana Filed Dec. za,19 s4,se No. 477,294

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This invention relates to a composition :for the generation of gas, said composition containing ammonium nitrate as a principal gasvproducing agent. More particularly, the invention relates to a novel composition usable witha binder material as a shaped explosive. Specifically, the invention relates to a novel composition consisting essentially of ammonium nitrate gas-producing agent, a binder material, a catalyst for the pnomotion of combustion of the composition, and finely divided carbon to improve the combustion characteristics of the composition, particularly to increase the burning ratethereofito which composition may be added an aliphatic acyclic oxime. More specifically, the invention. relates to a shaped explosive grain consisting essentially of the above components.

Ammonium nitrate is :widely used as a component of high explosives, particularly the so-called safe explosives. Even though classified as a high explosive, ammonium nitrate is extremely non-sensitive to ordinary heating and to shock and cannot-be detonated readily by local application of heat or by a blasting cap. Furthermore, when ignited, ammonium nitrate does not burn uniformly and has a tendency to go out when used in the absence of combustible organic material. Thus, to improve the burning quality, .to increase the sensitivity, and to utilize the excess free-oxygen made available by the decomposition of the ammonium nitrate, organic materials which also may function as binder material for the shaping: of the ammonium nitrate into grains are admixed with ammonium nitrate. The choice of components of binder material mustbe such that satisfactory combustion of. the propellant grain with respect to burning rate under conditions of use can be realized.

. Modern warfareutilizes large quantities of rockets for ground-to ground missiles, ship to-shore missiles, air-toground missiles, and air-to-air missiles. These rockets are comprised essentially of thin wall casings, which contain a combustion chamber in which is incorporated a quantity of solid propellant, a nozzle through which the decomposition gases pass thereby to create the ion-ward thrust of the missile, ignition means for igniting the propellant grain, stabilizing vanes and a war head which contains high explosive. Military rockets heretofore have utilized double-base powders such as ballastite as a solid propellant for .use in such rockets. Rocket units have also been developed to assist in the take-off of heavy loaded airplanes and to make possible the use of short runways. Such units are commonly known as JATO (jet assisted take-off) or ATO (assisted take-off) .units. A constant uniformly distributed assist impulse with respect to time is desirable for such take-oif service. and burning rates of the propellant material for use in such takeotf service are usually the range of item about 0.10 .to 0.16 inch of propellant grain per second at about 1000 pounds per square inch pressure. The

present invention is concerned primarily with propellant material for rockets, said propellant material having burning rates above about 0.16 inch per second at 1000 though the rate of burningis below that of detonation. Economic considerations of cost and availability make make the use of ammonium nitrate as the basematerial insolid propellant tor rockets and ATO quite attractive. Moreover, the relative low flame temperature of. the decomposition of ammonium nitrate. (17 302 2150 C.) makes desirable the use of ammonium nitrate. The availability of free oxygen from the decomposition of the ammonium nitrate permits theuseof oxidizable material in the binder material, the combustion of which enhances the energy available from the decomposition 0t the nitrate. Certain characteristics of ammonium nitrate require development of suitable associated material in. the compositionv to make ammonium nitrate suitable as a gas-generation means for rocket service or for take-off service. p i

Solid ammonium nitrate exists in several diiferent dorms depending upon. the temperature'of the nitrate and in. passing from one solid form to a difierent solid form, particularly at temperatures of about 3 2 C. and also --l8 C. i.e., temperatures common'tostorage conditions, a considerable volume change takes place in the ammonium nitrate. Thus thebi nder materialzused with the ammonium nitrate to form. physically stable grains must be flexible to compensate for changes in volume in order that such volume'changes will produce a minimum amount of voids and cracks inthe grain. Moreover, the solid propellant grain suitable ior'military use must be ballistically stable after prolonged storage at temperatures as high as 77? C. and as low as about '6 0 C. Production of fissures in .the grain either inter nally or externally over the surface of the grain creates additional burning surface which results in unpredictability of the ballistic performance of the rocket or ATO unit. Thus it becomesnecessary to provide a binder material which will provide a shaped grain of satisfactory physical stability. Furthermore, such grain mustbe capable of being ignited at extremely low or relatively high temperatures after being subjected to variable storage temperature conditions and to burn evenly and at such a rate as to distribute the impulse energy in accordance with the servicerequired.

Finely powdered ammonium nitrate contains about 20% or more by volume of void space and-this void space must be completely filled in order to obtain a shaped explosive grain of the desired physical characteristics. Moreover additional void spaceis produced when using an inorganic compound as the catalyst and the binder must not only fill the voids of the ammonium nitrate, but also the voids present in the finely powdered inorganic catalyst material. Another factor which contributes to the maintenance of uniform and smooth combustion-of the propellant grain is that ofstoichiometric oxygen balance for the production of water, carbon monoxide and carbon dioxide in the combustion of the pro pellant grain. Hence, binder material components capable of furnishing a part of the oxygen for combustion of the grain are used to supply any oxygen deficiency in the composition; r

For such military uses as rocket propulsion and ATO service, an explosive is desired which has non-detonating characteristics rather than the detonating characteristics of ordinary ammonium nitrate explosives. The burning characteristics of non-detonating explosives are dependent upon the temperature and pressure in the combustion chamber. The relationship of burning rate and pressure at constant temperature is expressed by R. N. Wimpress in Internal Ballistics of Solid Fuels in Rockets (1950), as i wherein B is the linear burning rate at pressure "p, 9 is the linear burning rate for the composition at 1000 p.s.i., p. is the pressure in p.s.i. in the burning chamber and nis. the pressure exponent showing dependence of burnihg' rate on pressure and is the numerical value equal toj the slope of the curve of burning rate in inches per second obtained by plotting the] burning rate at various pie sures. on'log-log'paper. Ammonium nitrate compositirons' u'sua'lly have. a pressure exponent of about 0.7 or higher. Smokeless powders, such as ballast'ite and cordite halve.- pressure exponents. between about. 0.6- and 0.7. A composition. having a pressure exponent. of the. order of ll'readil y passes. into detonation with only a small amount of shock. The lower the value of n the less is the detonating'; character of the decomposition of a gas-producing. composition and the more even and smooth is the burningrate of. the propellant grain. Thus, a sustained thrust; ra'ther'than a detonation-is obtained by smooth burning of the grain. Propellant compositions having an exponent less than about 0.65 are preferred and these propellant. compositions for use inv rocket service should have burning. rates of at least. 0.16 inch per second at 1000 pounds pressure.

'Anobject of this inventionis the preparation of a gas generating. composition for use in. rockets, the principle gas gen'e'rating material of said composition being am.-

moniumnitrate. Another object ofthe invention is the preparation of an explosive grain. having. a high burning rate. which grain is dimensionally stable and non-fissuring over a wide range of storage. temperatures. Still another object. of the invention. is the production of an explosive grain having a high. burning rate and a moderately low pressurev exponent, which explosive grain is suitablev for usein military rockets. A stillv further object of. the invention is to produce an ammonium nitrate-combustible binder material grain which will ignite at relatively low temperatures and pressures. An additional object of the invention is to produce a combustible ammonium nitrate propellant grain, the pressure exponent of the burning rate of. which. grain is desirably less than about 0.65 and the burning rate of which. grain. is desirably at least about 0.16 inch. per second at 1000 pounds pressure. Other objects will. become apparent from the description. of the invention. hereinbelow.

We have discovered that a gas-producing propellantgrain composition consisting essentially of a hereinafter defined mixture containing a major proportion of amrnoniurn nitrate; a Prussian blue combustion catalyst, finely divided carbon. and a plastic binder consisting essentially of cellulose acetate plasticized with a 2-component plasticizer consisting of a nitrodiphenyl ether and a liqid. polyester condensation product of a dihydric alcoho-l. and an aliphatic oxydicarboxylic acid has a relatively high burning rate and is physically stable with respect to non-development of fissures when subjected to wide. ranges of storage. temperatures. To this composition. may also be added an aliphatic ketoxime or ketodioxime to improve the burning characteristics; of the grain. with. respect to ignitability at low temperatures and with respect. to improving the pressure exponent of the-propellant grainqas described above. We have found that the incorporation of finely divided carbon in the composition. imparts. greatly increased burning rate thereof without adversely attesting the improvement in pressure exponent accomplished. by incorporation of the oximetin the grain composition.

Brieflyg. our -gas :-producing propellant composition consistsessentially of:

4 1 divided carbon will pass through a US. Standard sieve, prefer-ably through a #200 US. Standard sieve and more preferably through a #325 US. Standard sieve; and

(4) From about 10% to about by weight of a plastic binder consistingessentially of:

(a) Between about 18%'and"40% by weight of eellu lose acetate whichanalyzes from about 51% to 57% by weight. acetic acid; and

' (b) From about60%- to about 82% by weight] of plasticizer component's consistingessentially of: V

(i)' The liquid polyesterification condensation product obtained by reacting. one mol :of. an aliphatic oxydicarboxylic acid containing 4. to 6 carbon atoms per molecule with from about 11081no'ls to about 1.3 mols of at least one dihydric alcohol selected from the class consisting of ethylene glycol, propylene glycol, polyethylene glycol ether, polypropylene glycol ether and mixtures thereof which others and mixtures thereof have an average rnoiecnlcr weight not more than about 200 and which po'lyesterification condensation productisessentially anhydrous and hasan everage molecular weight of about 250 to about 1000;.and

(ii) At least one nitrodiphenyl ether containing from i one to three nitro groups per molecule and substantially wherein R and R are selected from the class consisting of methyl, ethyl and hydrogen, wherein X is selected from the class consisting of oxygen and NOH and wherein y is an integer from 0 to 2.

CARBON COMPONENT The carbon component of thepropellant grain when used in amounts of from about 0.5% to'about 7% by .(.'.1),At least. by" weight of ammonium nitrate,

weight of the grain increases the burning rate by about 0.01 to about 0.07 inch per second depending on the type and amount of carbon used. We prefer to use from about 1% to about 3% by weight of carbon in: the-composition. Carbon in excess of about 7 is undesirable because the slight increase. in burning rate is more than counterbalanced by the smokiness imparted to the combustion gas stream.

The carbon. component of the propellant composition which. we add to. increase the burning rate includes finely divided; highly adsorptive activated. carbons; These are well known in. the art of decolorizing sugar and adsorption of gases. Examples: of these. are Noriti and Nu.- char, the former being a highly-adsorptive*activated carbon used. to adsorb odors, and to decolori'ze. water, gases, chemical solutions, oils and greases. Nuchar .is an" activated carbon made from. a residual organi material obtained in the manufacture of cellulose and is characterized by high porosity resulting in high adsorptive capacity. Like Norit it is used as a decolori-zing and deodorizing agent. r Y

A. second general class of carbon. useful for increasing theburning rate of the propellant composition are the carbon blacks. These are roughly classified as channel blacks prepared by the impingement of small natural gas flames, furnace combustion blacks-produced by the partial combustion of essentially gaseous hydrocarbons in; closed retorts and. furnace thermal blacks. produced: by: thermal decompositionof hydrocarbons such as. acetylene: in preheated: furnaces. .The carbon. blacks are characterized lo'w ash. content,- by having ext'remeiysmall particle size;. that. is, SQ-t'o 5909 A.,.' and contain. adsorbed hydroe of the invention. characteristics and their effectiveness in raising the bumgen and oxygen.- Other carbon blackswhich may be used in the propellant grains are lamp blacks produced by burning liquid fuels such as petroleum oils, tars and aromaticresidues in specially designed pans, combustion taking place under restricted air supply conditions. The carbon blacks as indicated above are generally characterized by exceedingly small particle size, that is, well below #325 US; Standard sieve particle size. However, to avoid dusting and convenience in handling, some carbon blacks are formed to the so-called bead type carbon blacks which beads are generally of such dimensions I as to pass through a'# 20 U.S."Stan'dard sieve and are retained on a #200 US. Standard sieve. The beads are very soft and arephysically unstable as beads and become disintegrated to smaller than #325 US, Standard sieve during the mixing and milling of the composited propellant components as described hereinbelow. The carbon blacks are of low ash content, and usually'contain less than 0.5% ash. Examples of bead typecarbon blacks are Micronex'Beads (channel blacks) and Statex Beads (furnace blacks).

A third typeof carbon which is usefulfor improving the burning rate of our gas-producing propellant compositionis graphite, flake and amorphous. If derived from a natural graphite, the ash content should be reduced below about 5% which can be accomplished by treating the natural product by air flotation or the ash content may bereduced by leaching with mineral acid or by other methods well known to the art. We prefer graphite of colloidal or semi-colloidal particle size.

Still another type of carbon which wehave found effective for increasing the burning rate of the gas-forming composition is finely ground petroleum coke, particularly petroleum coke obtained as a residue in the pipe-stilling of Mid-Continent heavy residuums. Such coke usually contains less than about 1% ash and is preferably pulverized to pass through a #325 US. Standard sieve prior to incorporation in the gas-producing propellant composition. The coke may be activated by methods well known to the art to improve the efiiciency thereof as a burning rate promoter in our propellant composition.

The carbon component of our composition contains not more than about 5% of ash in a finely divided state. Particularly suitable classes of carbons commercially available are activated carbon (active carbon or activated charcoal), carbon black, petroleum coke and graphite.

.In general, the finely divided carbon will pass through a #20 US. Standard sieve.

ticle size to pass through a #325 US. Standard sieve or which is readily reduced to such a size during the milling operation utilized in the preparation of the composition Because of their uniformity in physical ing rate, the commercially available carbon blacks are a preferred source of the carbon utilized herein. Activated .carbons containing not; more than about 3% ash are another preferred source of carbon for use herein.

AMMONIUM "NITRA'FE a The term ammoniumnitrate as used in this specification and in the claims is intended'to mean either ordicommercial grade ammonium nitrate, such as conventionally grained ammonium nitrate containing a small amount of impurities and which is then generally coated with a small amount of moisture-resisting material such weight of ammonium nitrate.

PRUSSIAN" BLUE CATALYST j It hasbeen discovered that certain iron compounds are effective catalysts for the combustion of ammonium nitrate and ammonium nitrate-oxidizable material mixtures. These catalysts are the subject matter of US." patent applications filed by Wayne A. Proell and William G. Stanley, Serial No. 273,564, filed February 26,1952, and Serial No. 288,065, filed May 15, 1952. All of the combustion catalysts disclosedin thme applications contain the iron'cyanide radical, either ferrocyanide or ferricyanide. In addition to the iron cyanide radical, these catalysts contain a second iron ion whichfmay be either ferric or ferro(us). In addition to the iron-iron cyanide complex, the catalyst may contain alkali metal. and/or ammonium ions. It has been found that the generic classes of iron-iron cyanide compounds known as soluble Prussian blues and insoluble Prussian blues are eifective catalysts for the purposes of this invention. It is known that the better soluble Prussian blues contain alkali metal(s) such as potassium and sodium and/or the ammonium radical. Some of the compounds which have been found to be effective are: ferro ferrocyanide, ferric ferrocyanide, ferro ferricyanide, ferric ferricyanide, potassium ferric ferrocyanide, sodium ferric ferrocyanide,

ammonium ferric ferrocyanide, potassium soluble Prussian blue, sodium soluble Prussian blue and ammoniumsodium soluble Prussian blue. i i i These applications show that the so-called insoluble Prussian blues, either the chemical compound ferric ferrocyanide, or the commonly known insoluble Prussian blue, are more effective catalysts at high pressure operation than are the soluble Prussian blues. Thus when operating the combustion chamber containing the solid propellant at pressures between about 500 and 2000 p.s.i. a higher burning rate, in inches per second, is obtainable when using a given composition containing insoluble Prussian blue as the catalyst than is obtainable when using the same composition using soluble Prussion blue as the cataylst. The insoluble Prussian blue containing explosive compositions are difiicult to ignite at atmospheric pressures when the amount of catalyst present is less than about 6 weight percent. However, these compositions ignite readily when an elevated pressure is imposedon the combustion chamber prior to the application of the igniting means. a

An application, Serial Number 288,549, filed May 17, 1952,.by Wayne A. Proell, discloses that ammoniated insoluble Prussian blue is an effective catalyst for the combustion of ammonium nitrate or ammonium nitrate-oxidizable material mixtures. The ammoniated insoluble Prussian bluecatalyst possesses the ignition characteristics of the soluble Prussian blue catalyst and the burning rate characteristics of the insoluble Prussian blue catalyst. When used in the mixture in amounts of about 3 to 4%, the ammoniated insoluble Prussian blue catalyzed mixture is hard to ignite and does not sustain combustion in an inert atmosphere. The ammoniated insoluble Prussian blue catalyst is produced by exposing an insoluble Prussian blue to the action of ammonia gas. The temperature of the reaction zone containing the insoluble Prussian blue and, ammonia gas increases rapidlyuntil a temperature ofabout 60 C. is reached; as the temperature increases, the rate of increase decreases until at about 60 C. a plateau is reached. As measured by temperature increase, the interaction of ammonia and the insoluble Prussian blue is believed to substantially stop when the temperature of the reaction zone reaches the plateau of about 60 C. The ammoniated insoluble Prussian .blue hasa strong odor of ammonia after beingcooled to room temperature. An ammoniated insoluble Prussian blue of catalytic activity about equal to the 'odorous material which does not possess. any appreciable ammonia odor can be obtained by maintaining the odorous material at a temperature of about 70 C. for several hours. The

ammoniatiorr of the insoluble Prussian-blue does not change the physical appearance of the material and is noticeable principally in that thecataliytic activity ofthe insoluble Prussianblue, particularly at low operatingipres sunes, is 'markedly' improved. By this treatment. various catalytically active grades of insoluble Prussian blue can be converted tomaterials having about. equalicatalytic activity; i.e.-,.-the'nom1al variation in catalytic. activity of Prussian. blue obtainedyfronr diffcrentmanutacturers can be, eliminated by this-ammoniationprocedures The term fammoniateddnsoiuble Prussiansbluel" is intended to include both; the ammonia-odorous material, and the substantially odor-free material.

, An application, Serial Number 287,623, filed May 13, L952, by WayrreA. Proell-,discloses that alkali metal-iron cyanide and ammonium-iron. cyanide are effective catalysts fbr'sensitizingthe ignition and combustion of ammonium nitrate-base explosives. Particularly effective are potassium ferricyanide and ammonium ferricyanide. These iron. cyanide catalysts are not as effective when used in compositions containing oxygenated oxidizable materials as are the iron-iron cyanide complexes, the solu-' ble Prussian blues, the insoluble Prussian blues and the ammoniated insoluble Prussian blues.

' When using any one. or a mixture of iron-type catalysts defined above, between about 1% and 8% by weight, preferably about 2% to about 4% by weight. of catalyst based on the total weight of the grain is used.

I BINDER The binder material of thev gas-producing. propellant composition consists essentially of cellulose acetate plasticized with:

(a) The liquid polyesterification condensation product obtained by reacting an. aliphatic oxydicarboxylic acid containing 4 m6 carbon atoms per molecule with. a dihydric alcohol; and

(b) At least one nitrodiphenyl ether containing from one to three nitro groups per molecule and substantially not more than two nitro groups in any benzene nucleus.

The cellulose acetate used in this invention. is known. as a partially-esterified cellulose acetate and is described as having an acetic acid content between about 51 and 57% by weight of acetic acid. The term percent by weight of acetic acid denotes the amount of acetic acid obtained on saponification of the cellulose acetate and is expressed as percent of the initial material. A particularly suitable celluloseacetate is lacquer grade, that is, a lacquer grade which analyzes between about 54 and 56% by weight of acetic acid. Lacquer grade cellulose acetate is described inaddition to its acetic acid content by its viscosity, when dissolved in acetone, as between about 2 and 80 centipoises at 25C. Hereinafter, the term viscosity as appliedto cellulose acetate denotes the viscosity of an acetone. solution containing 20% by weight of a cellulose acetate. The preferred cellulose acetate of this invention analyzes between about 54 and 56% by weight of acetic acid andhas a viscosity within the range of about 2 to 10 centipoises. A binder having the proper characteristics for. use in preparing the shaped exposive composition of this invention contains about 18 to 40% by weight of the defined cellulose acetate. Prefer-ably, the binder contains between about 18 and about 25 of the defined cellulose acetate.

The plasticizer utilized in the binder of thisv invention consists essentially of a combination of two plasticizers, one of which is a liquid polyesterification condensation product obtained by reacting an aliphatic oxydicarboxylic acid containing 4 to 6 carbon atoms per molecule with an excess of at least one dihydric alcohol selected from the class consisting of ethylene glycol, propylene glycol, polyethyleneglycol ether, polypropylene glycol ether and mixtures of ethylene glycol ether with propylene glycol ether, which ethers and mixtures. thereof have an. average molecular weight of not more than about 200. Polyethylene glycoleZQQ, which. is a. mixture of tetraethylene-glycol and pentaethylene glycol which may contain a minor amount oftriethylene glycol, but which mixture is.- predominantly tetraethylene glycol, may also be-used as the dihydric alcohol. A suitable. aliphatic oxydicarboxylic acid for condensation with the polyhydric. alcohol. is diglycolic acid. Other .o'xydicarboxylic: acidswhich may .be used are oxyacetic-propanoic acid. and oxydipropanoic-acid.

We. prefer to esterify diglycolic acid with ethylene glycol and the polyesterification condensation product. is essentially anhydrous and has. an. average moleculanweight of? about 250 to aboutlQOO- The preferred. polyesterifica tion-product. obtained .by reacting, ethylene glycol with diglycoli'c'acid will'usually have a viscosity (S.U..S.). of

from about 400 to about 600 seconds. at 2101" FL We prefer a polyesterificat-ion condensation producthaving an average molecular weight within the range of about 35.0 to about 600- as taught in. thecopendirig application of Norman 1. Bowman and Wayne A. Procll, entitled Polyester Plasticizerfl filed November 30, 1954, Serial No. 471,992, now abandoned. Mol ratios of dihydric. alcohol to the oxydicarboxylic-acid in the polyesterification reaction mixture are preferably within the rangeoi from about 1115 1.25 to 1.0. In preparing the polyesterification product the. oxydicarboxylic acid" is dissolved in the dihydric alcohol and the solution is heated, preferably in a 2-stage thermal treatment, the first stage being carried out at temperatures below about 150 C. and in the. final I heating stage temperatures within the range of irom about 150 C. to about 200 C. are used. Theextentof-polyesterification is controlled by adjusting the factors of time, temperature and pressure at Whichthe polyesterification is carried out and. at least 70% of the water theoretically producible for complete esterification for the alcoholacid charge is withdrawn. The amount of water withdrawn from the polyesterification mixture during theheating thereof is. used as a measure of the progressof. the polyesterification to completion. The heating of. the reaction mixture is usually for a total time of at least six hours up to thirty hours or more. At least a part of the final heating stage maybe carried out under reduced pre's- Essentially anhydrous polyesterification tion reaction as indicated from theamount of, water withdrawn from the reaction zone; and

(3) On the molecular Weights of the dihydric alcohol :and the oxydicarboxylic acid introduced to the polyesterification reaction zone.

H Preferably, the reactionv is carried out to not less than. completion as based on the water theoretically producible. The term water theoretically producible as used herein is defined as' two mols of water per mol of aliphatic oxydicarboxylic .a'cid charged to the polyesterification reaction zone. Ingen- 'eral,.-the greater the excess of dihydric alcohol nsed'in the reaction'rnixture, the "higher isthe percent completion of the reaction. Thus, for a 20%mol percent excess dihydric. alcohol in the reaction mixture, the reaction is carried out to -95% completion and when 30-mo1 percent excess dihydric alcohol is used, the 'esterification should be. carried out to l00% completion.

The other plasticizer component of the binder .is a nitrodiphenyl ether, preferably nitrodiphenyl ether containing as an average abouttwo nitro groups per mole cule although nitrodiphenyl ethers containing from one to three nitro groupsper molecule may be used. Substantially not more than two nitro groups'a're presentp'n any benzene nucleus, and as an average less than'about 2.5 nitro groups per molecule ofnitrodiphenyl etherare present when a mixture of nitrodip-henyl ethers is. used. We preferto use as the second plasticizer component 2,4-dinitrodiphenyl ether which may be prepared in high yields by reacting phenol with 2,4-dinitrochlorobenzene as described in copending application ofWayne A. Proell and Norman J. Bowman entitled Thermoplastic Compositions, filed October 27, 1954, Serial No. 465,- 132. Mixtures of nitrodiphenyl ethers may be prepared from diphenyl ether by methods well-known in the art, using either fuming nitric .acid or mixtures ofconcentrated nitric acid and concentrated sulfuric acid as nitrating agent. Commercial products consisting of a major proportion of diphenyl ether and a minorproportion ofdiphenyl may be used as the intermediate for nitration in the preparation of the nitrodiphenyl ether plasticizer component of this invention. Dowtherm A. which is a eutectic mixture containing about 73.5% diphenyl ether and 26.5% diphenyl is such a commercial product and may be used for the production of mixtures comprising mononitrodiphenyl ethers with dinitrodiphenyl ethers and mixtures of trinitrodiphenyl ethers with these nitrodiphenyl ethers containing less nitro substituent groups than trinitrodiphenyl ethers. The term mixtures of mononitrodiphenyl ether and dinitrodiphenyl ether and mixtures of the foregoing with trinitrodiphenyl etherfand in general, the term nitrodiphenyl ether is used in this specifi cation and in the claims to include nitrodiphenyl ether and mixtures of nitrodiphenyl ethers produced from Dowtherm A. .Such -nitrodiphenyl ethers'will contain minor amountsof nitrodiphenyls. U i I .As indicated hereinabove, the proportion of binder material in the gas-producing propellant composition is within the range of fromabout to about 25% by weight of the composition. The binder material consists of from about 18 to about 40% by weight of the cellulose acetate and from about 60% to about 82%. by weight'of the plasticizer components. The ratio (by weight) of polyesterifica-tion condensation product plasticizer to nitrodiphenyl ether plasticizer in the binder is within the range of from about 1:4 to 4:1. We prefer about equal percents by weight of these two plasticizers in the binder material.

OXIME COMPONENT As indicated hereinabove, we prefer a gas-forming propellant composition containing an aliphatic acyclic oxime which is added to the binder composition for the purpose of improving the combustion characteristics of the grain material with respect to the pressure exponent. The amount of oxime incorporated in the gas-producing composition is from about 1% to about4% by weight of the composition and preferably between about 2% and 3%. Oximes corresponding to the formula as defined above are preferred. Examples of such oximes are acetonylacetone dioxime, acetylacetone dioxime, acetonylacetone monooxime, and succinaldehyde dioxime. These oximes are particularly eifective for depressing the pressure exponent of the defined explosive composition with which they are associated and are also effective in promoting ignitability of the compositions at extremely low temperatures. The oxime component is added to the molten binder material prior to the addition nitrate and binder are subjected in completing the fabrication is complete, the mixture is cooled and-stirred until the reaction mixture comes to room temperature. The oxime precipitate is filtered from the aqueous mixture and dried after washing with a small amount of water. Acetylacetoneoximes may be prepared in similar manner using acetylacetone intermediate.

In preparing the compositions of this invention, the binder material is first prepared, thegoxime being then thoroughly mixed with the binder after which the am monium nitrate; carbon and catalyst are milled with the binder. The binder is prepared by heating the plasticirler material at a temperature not in excess of about 150 C., usually within the range of from about"120; C. to

about 140 C. The heated plasticizer material that is,

the mixture of polyesterification condensation product;

for example ethylene glycol diglycolate, and nitrodi phenyl ether, is stirred and the cellulose acetate is added; heating and stirring being continued until a homogeneous mixture is obtained. The oxime is then added to the mixture and is thoroughly mixed therewith before the addition of the thoroughly mixed ammonium nitrate, carbon and the-catalyst components of the finished grain. The catalyst may be added, mixed with a part of the ammonium nitrate or it may be added immediately pre ceding the addition of the ammonium nitrate. The ammonium nitrate, carbon and catalyst are then milled into the plasticized mass at a temperature below about 120 C. and preferably at a temperature of about C. If desired, the carbon may be added and milledwith the plasticized binder containing the oxime (where oxime is a component of the grain) before milling the ammonium nitrate and catalyst into the composition. Milling is continued until a product of uniform texture isobtained. Burning rate test strips are extruded ormolded under pressure and the material is shaped into propellant pellant compositions the results of burning tests of which as given in Tables 1 and 2 below. u M PREPARATION OF PROPELLANT COMPOSITIONS A mixture of 34.64 parts by Weight of 2,4-dinitrodiphenyl ether and 34.64 parts by weight of ethylene glycol diglycolate, prepared according to the procedure de scribed hereinabove, was added and stirred at a temperature within the range of 120l40 C. to obtain a homogeneous mixture of the plasticizer material. To this mixture was addeda total of 20.72 partsby weight of cellulose acetate (LL-1 lacquer grade) which analyzed between 54 and 56% by weight of acetic acid. The cellulose acetate was added in small portions during the stirring of the plasticizer and when all of the cellulose acetate had. become plasticized as indicated by a homogeneous molten product, the molten product was cooled to the range of -120 C. and 10 parts by weight of acetonylacetone dioxime was added. The oxime was incorporated in the plasticized mass by rapid stirring to form a homogeneous binder including the oxime. These 100 parts byweight constituted 23% by weight of the total grain composition and the binder components of these 100 parts, that is, 90 parts, constituted 20.7% of the total grain composition.

The ammonium nitrate used in fabricating the gasreceived) wasof such. particle size as to pass substantially completely. through. a. #35 [1.8. Standard sieve. Theground-material, was recombined with thefung roun'd material and. thoroughly mixed therewith to: giveammonium nitrate, of. small. particlesize, at least 75%. of which would pass through a #325 U..S. Standard. sieve.

The. ammonium nitrate was then. divided into portions of. onerthird. and two-thirds of the total of ammonium nitrate-to be usedv in the. grain. The finely divided carbon black. in: an amount. of from 1 to- 5% of the total grain composition and; the insoluble Prussian blue catalystwcref then thoroughly admixed with the one-third portion=of the, ammonium: nitrateto-be used. The binder material containing, the oxime was stirred at 110 to- 1'20 Chi-n. a sigma blade mixer. The. one-third portion of ammonium nitrate containing the carbon and Prussian, blue-catalyst were then added rapidly and the mixturewas. milled for from to minutes, the tem perature of the mixture. being maintained between about 110 and 120 C. At the end of this 15-20 minute period the remainiugtwothirds portion of the ammonium nitrate was-added and milling was continued for an additional to 45 minutes. The last, 15 minutes of this mixingperiod was completed under a vacuum of at least 1 .5 inches of. mercury. Homogenization was complete at the endof. this milling. period. I

The. grains and. burning test strips produced from tlns material fabricated as described below had the following approximate composition:

The remainder essentially all ammonium nitrate.

Wherethe amount of carbon added to the composition amounted to 1% by weight, the ammonium nitrate content of the grain. was about; 73%. When. 5% of carbon was included inthe hinder, the, percent ammonium nitrate in the finished grain was about 69%.

Burning. irate test strips of the above material were formed by subjecting the material contained in a 1 diameter cylinder to 2,000 pounds pressure and extruding therefrom through an aperture a strand of. about diameter. The composition of this invention flows fair- 1y readily at temperatures above about 100 C. and becomes dimensionally stable at temperatures below about 90 C. This characteristic simplifies the problem of forming the test strips and also the grains since it elimihates the necessity for accelerated cooling of the mold or the extruded grain. The composition of the explosive of the invention has another distinct advantage over conventional solid propellant compositions. It was found that defective grainscan' be reworked alone or in admixture with. fresh materials to produce satisfactory grains. The reworkability of rejects results in a substantial saving over conventional grains where: rejects cannotbe reworlred.v The. material was maintained at a temperature of about 110 C. during the ram extrusion of the strand.

After.cooling,,.the= strand was cut into test strips approxi.- mately 5.-" long and these were then coated with lacquer grade cellulose acetate to inhibit surface burning along the strand. The test strip was drilled at two points 3" apart along its length and fusible wires .were inserted in the drilled holes. The test piece was then placed in a pressure bomb, electrical connection of the fuse wires being made to a timing device. The timing device was started by the fusing of one wire and as the test piece burned along its length the timing device was stopped by the fusing of the second wire. Thus the timc'for burning of the three inches of thetest piece was obtained. Thetestpiece was ignited by means of a. Nichrome resistance wire placed in contact with one end of the test piece. Burning rates for the. test pieces were determined at pressures of 600, 800, 1.000,. 1200', 1.400,. 16.00; and 1800 pounds per-squareinch of nitrogen pressure. Burning rate in inches. per second for the dilierent pressures was, plotted on log-log paper. The plot gave the straightline relationship. The slope of this line is defined as the pressure exponent of the. burning rate. Burning rates ofv the materials in this. specification are. defined as burn ing rates at 1000 pounds. nitrogen pressure.

In the preparation of shaped propellant grains of the gas-forming material the hot mass was loaded into a 2% diameter, mold, maintained at a temperature of about C. Temperatures 'above about C. are avoided in. the milling and molding. of the. ammonium nitrate-containing grain in order to'miniini z'e the poss'i bility of heat ignition of the composition under conditions of milling and molding, The mold in which the material is loaded is provided with an inset which may be of one or more different shapes. Thus the inset provides the grain with longitudinal. aperture'in the form of a cross, star, triangle or other shape to provide uniformly distributed. internal burning. surface. The grain may be tubular in form as. illustratedinFiguresl and 2.

Uniform internal burning surfaces may be provided by a multiplicity of insets. in. the mold. The propellant. composition, rnay also be molded into disc-shaped grains, preferably perforated for use in rockets and mi'ssiles.- Discs ofthe material are suitably spaced in the roe ret case to provide uniform combustion of the discshaped lgrains. In molding the material into grains the mold was subjected to 10,000 p.s.i. ram pressure for about five minutes after which the ram pressure was reduced to 5000 psi. This pressure was, maintained for an additional fifteen minutes. The mold was removed from the press and allowed to cool to room temperature. The grain was removed from the mold and cut to 4" lengths. The exterior surface of the grains was inhibited to prevent surface burning by coating with Vistanex-asphalt mixtures. Other non-burning material such as cellulose acetate, ethyl cellulose acrylijc plastics and so forth may be used.

Grains of the above composition containing activated carbon, that is, Norite A. as the finely divided carbon component in the above composition were cycled through severe temperature changes in order to determine the resistance of the grain to fissuring. In this test, the grain was placed in a cabinet for aperiod of two hours, which cabinet was maintained at a temperature of 80 C. At the end of the two-hour period, the grain was removed and placed in a cold cabinet maintained at a temperature of -60 C. for a period of two hours. This complete cycle of extreme temperature change was followed immediately by a second cycle wherein thegrain was again subjected to the temperature of 80 C. for two hours followed by a two-hour period in the 60 C. cabinet. Following this two-cycle temperature treatment, the grain .was permitted to come to room temperature after which it was examined for external fissures and the condition of the internal structure, of. thegrain, with re spect to fissures, was determined by testing the grain in a miniature; rocket motor. The grains so cycled showed no variation, with respect to burning properties, from similar grains which had not been subjected to the temperature cyclingtests. v I

The grains prepared as described above were tested for burning "properties in; a miniature rocket motor. motor consisted essentially of a cylinder closed at one end and threaded at the open end. The straight side of the cylinder was about 8 inches long and the cylinder had an internal diameter of about 3 inches. A funnel shaped portion provided with an opening for the attachment of a. nozzle and provided with threads at the larger and was threaded onto. the cylindrical casing to complete the combustion chamber of the motor. Various sized orifices wereprovided in order tolperrnit the operation of the motor at difierent combustion chamber pressures; These orifices varied from 0.17 to 0.24 inch in diamwith which itis associated in the composition.

Table 1 i Burning Experi- Carbon (Percent) Oxime (Percent) Rate Pressure ment I (Inches/ Exponent See.

None None 0.14 ca 0.8

. None 1. Acetgnglacetone Dioxime 0.14 0.58 Norit A 1%) 0.19 0.60

Norit A 1 (5% 0.22 0.60

garbon Blaock k ($851 75.-- 0.19 0. 65

e r0 eum 0 e {Carbon Black 2 (0.2%

Commercial grade Norit activated carbon. Particle size less than #325 sieve. Ash

content 3.27%

eter. By varyingthe orifice size, the combustion chamber pressure could be varied from about 700 to about 2000 p.s.i. l 3

In the combustion of:a grain containing no internal fissures the-pressurejat the initial stage of the combustion rises. rapidly to a level within the range. of from about 700 p.s.i., to 1000 p.s.i., and remains at such level without appreciable variation during the combustion of the entire grain. Any irregularities such as fissures in the grain, internal or external, cause irregular fluctuation in the pressure developed by the combustion of the gram.

In order to reduce the amount of explosive material needed per motor test, a perforated cylindrical aluminum slug was used to take up about half the longitudinal volume of the motor. Thus in operation the motor contained the slug and a. 2.5 inch diameter-perforated grain 4 inches long.

The grain was ignited by a black powder mixture, which mixture was in turn ignited by means of an electrical squib. It was found that satisfactory ignition could beobtained by using 25' g. of' the following mix- .ture: sparkler' -powder, 10g.;.FFG gun powder, 7.5 g.; and FFFG powder, 7.5 g. This mixture was placed at the nozzle endof the funnel-shaped member and was held in place by'meaps of a paper disc pressed firmly against the sloping sides of the member. The motor was assembled by inserting into the casing first the aluminum slug and then the grain to be tested. The test grain was inhibited on the exterior surface and the annular ends by coating with Vistane'x-asphalt mixture. This inhibiting the total exterior of the grain results in the burning of the internal surfaces only. The nozzle end complete with powder igniter was then screwed to the casing. The electrical squib was then inserted through the-nozzle opening until it contacted the powder mixture. This method of arming the motoris particularly desirable because the motor is essentially inert until afew seconds before the test run is fired. It 'has been found that this method of ignition gives ignition delays between about l00 and 500 milliseconds.

The-results of burning tests of strand materials having compositions indicated above and fabricated as described above are shown in Tables 1 and 2. Burning rates for the compositions are "expressed in inches per second at 1000 pounds pressure of inert gas, that is, nitrogen. The catalyst used in these compositions was insoluble Prussian blue. The ammonium nitrateused in the compositions was finely ground to particle size such that the major portion, that is, at least 75% would pass through a #325 US. Standard sieve. We have found that this grade of ammonium nitrate when finely ground exhibits carbon showed greatly increased burning rates over thecompositions containing no carbon, and this increase in burning rate (about 35% for 1% carbon and approximately for 5% activated carbon in the composition) was accomplished without materially aifecting the value of the pressure exponent. Likewise, the burning rate of the composition containing 1% of carbon black showeda burning rateincrease of about 35% resulting from the presence of carbon black. The mixture of petroleum coke with the carbon black incorporated in the composition increased the burning rate about 20%. The burning rate of gas-forming propellant compositions containing cellulose acetate, 2,4-dinitrodiphenyl ether, ethylene glycol diglycolate, insoluble Prussian blue catalyst, acetonylacetone dioxime, ammonium nitrate and different types of finely divided carbon in equal amounts in the diflEerent examples, that is, 1% on the total weight of the strand material, and in proportion shown above withrespect to the components, is shown in Table 2. The ash content of these finely divided carbons is also included in the table. Included in the general types of carbon are channel blacks, furnace blacks, graphite and Nuchar (activated carbon).

Table 2; 7

Carbon Burning Rate Pressure Experl- (Inches/ Exponent ment 7 Type 1 Ash, See.)

Percent 7 None 0.14 0.58 8 Micronex Beads (W-B) 0.13 0.20 0.60 hannel). v Peerless Mark I1 (Channel)- 0.09 0. 19 0. 61 Statex) Beads (Fur- 0.53 0.20 0.58

nace a Continex Furnace Black 0. 50. 0.10 0. 54

(HAF). Continex Furnace Black 0.35 0.18 0.67

(HMF Corl ltigental Channel Black 0.15 0. 18 0.61 Witco Channel Black 0.15 0.17 0.6%

(MPR Graphite (Flake)-. 3. 52 0.16 0.65 Nuchar (C-lQO-N).- 5. 25 0. 16 0. 55

It is to be noted that the presence of ash in the carbon has little or no effect on the efliciency of the carbon for increasing the burning rate until the percentage reaches a figure above 0.5% ash. Thus graphite with an ash content of 3.52% increased the burning rate at aesaaar 1%-am1ount only-about 14% Nuchar which had an ash content of about 5% likewise was reduced in efliciency with respect to increasing the burning rate of the composition. The data with respect to channel blacks and furnace blacks indicate that samplesof the latter which contained about 0.5% .ash were of efliciency equal to; the

wing of an aircraft; normally at least two units, i. e., one.

under eachwing, will be used. flnFigure 1, thefbodyof the unit is made up of 'a tubularmember flwhich is closed at one end and which is "provided with threads at the open-end. Member 11 is provided with two loops, 12

and 13. These loops are used to hangthe unit from a carrier, not shown, which is attached to the wing of the aircraft. This carrier makes it pos'sibleto jettison the.

unit after take-off. A somewhat funnel "shaped member 14 is attached to member 11 by engagement of the threads atthe large open end of member 14 with the threads on member 11. Member 14 is provided'with a "nozzle 16 through which the decomposition products pass. The size of nozzle 16'determi'nes infpart the pressure maintained inside of the chamber formed by members 12 and 14.

' The solid propellant fills the cylindrical portion of member 11. The solid propellant "in this illustration consists of 'sevenjtubular grains, 1'7, 1 8, 19, 2 0, 21, '22 and 23; each having an CD. of about 3 inches and having a centrally located cylindrical opening 1 inch in diameter, the full length of thegr'ain; the grains are approximately 30 inches long. The. grains used herein consist essentially of Prussian blue catalyst, which may be insoluble Prusrsi'an bluecatalyst, binder, 'oxime, carbon and ammonium nitrate as described for grain compositions described above. Each grain has the annular areaat each end inhibited against burning by a coating of asphalt in order that the burning may take place on the cylindrical surfaces only. For some uses it is desirable to have a grain which burns cigarette fashion in which case the outer surface and one'end of the grain will be inhibited to prevent combustion.

. Although fat-ubular grain is illustrated herein, the in- 'vention is not limited to such a grain. Any particular sh'ape may be utilized. Examples of other shapes are cylinder, cruciform, t-ri'form, hexaform, octaform and slab "as described above, in the "case of perforated grains, the perforation may be circular or star-shaped with 'various numbers of points in the star. Furthermore, a singly cylindrical grain having one ormore longitudinal perforations may be utilized in some cases, instead of the multigrain unit shown. e 1

The grains are .held in longitudinal position and prevented by sliding back and forth in the combustion chamber by means of a wire grid 26. Wire grid 26 consists of a ring out to fit the threads of "member 14 and provided with a grid work of metal wires that will resist the high temperature existing'in the. combustion chamber.

On one side of the conical portion of member 1-4 there is provided for the combustion chamber a safety venting means 28. Venting means 28 comprises a tubular member fastened to member 14, which tubular member has full access to the combustion chamber and is provided with a rupture disc, not shown. The rupture disc is of such construction that excess pressure in the combustion chamber will blow out the disc, whereby the pressure in the combustion chamber will be held below the point of serious damage to the unit.

' An igniter means is positioned within member 14 so as to close off the nozzle 16.- The igniter means consists of a container 31 filled with black powder, or some other 515 easily ignited material, which canproduce alarge volume of gasses at elevated pressure. Aqsquib 32 for igniting the powder, is attached to the container 31 in communication with the powder contained therein. Electrical wires 53 connect a wire in the squib to the electrical system of the aircraft and a switch therein (the connections to the aircraft are not shown).

The -ATO unit is assembled as follows: The grains are inserted into member 11. Venting means 28 are fastened to member 14. Igniter 31 is inserted through the large open end and fitted so as to close the nozzle, the wires 33 having first been passed through the nozzle 16. The wire grid 26 is screwed into the large open end of member 14. The assembled nozzle portion is then secureiy screwed onto member 11.

The assembled unit is then attached to the wing of the aircraft by loops 12 and 13; wires 33 are connected to a the electrical operating assembly in the aircraft. When the pilot desires to obtain the assisted take-01f, he throws the switch which causes the current to pass through wire 33 and to heat up the firing wire in squib 32, which in turn ignites the powder in the container 31.

The container is of sufiicient strength to withstand the initial pressure generated by the gas'esfrom thepowde'r. The hot gases raise the pressure in the combustion cham ber high enough to permit the grain to ignite. The "combustio'n of the grai'n causes the pressure inthe'chambe'r to rise to 'a point which cannot be resisted by container 31. I

The container disintegrates and the pieces aredischarged through nozzle 16. The total time from throwing the switch to full operation of the unit'is onthe orderof less than 0.5 second.

As -the gases pass out of the nozzle the reaction acts on the aircraft and adds it's thrust to assist the aircrafts propeller; a marked increase in forward speed results and permits the aircraft to take on in a shorter space of time or it permits lifting a load heavier than could be airborne by the meet the propellers alone. I When using about 4 or "more of the iron-type catalyst, the grain willignite at relatively low pressures and no special precautions are necessary to maintain "elevated pressure in the chamber until ignition occurs, as shown above.v In this case, the igniter maybe introduced into the combustion chamber by a means attached to the conical portion of member 14 (this procedure is conventionally used and is illustrated in U.'S. 2,479,828) and no closure is placed on nozzle 16.

The conventional placement of the igniter may be used with the lower catalyst content grains. However, it is necessary to use a much 'heavierpowder charge in the igniter or, preferably, the nozzle is provided with a rupture disc, which is set to blow outat about 500 ;p.s.i.

Other-methods of igniting the grain can be readily devised. I

While the invention has been illustrated by an assisted Y will be in air-to-air missiles. I a

:We claim:

take-off operation it is probable that the prefer-rednse weight of ash and aplastic binder material in an amount within the range of from about 10% to about 25% by weight of said composition which bindermaterial consists essentially of (d) from abou't'18%- to about 40% by weight of cellulose acetate which analyzes from about 5 1% to about 57% acetic 'acid and (b) from about 60% to about 82% by weight of plasticizer components consisting essentially of:

(i) The liquid polyesterification condensationjproduct obtained byr'eactin'g one tool of an aliphatic oxydi- 52,9421eei carboxylic acid containing 4 to 6 carbon atoms per molecule with about 1.08 mols to about 1.30 mols of at least one dihydric alcohol selected from the class consisting of ethylene glycol, propylene glycol, polyethylene glycol ether, polypropylene glycol ether and mixtures thereof which ethers and mixtures thereof have an average molecular weight not more than about 200 and which polyesterification condensation product is essentially anhydrous and has an average molecular Weight of about 250 to about 1000; and

(ii) At least one nitrodipheuyl ether containing from one to three nitro groups per molecule and substantially not more than two nitro groups on any benzene nucleus,

wherein the ratio by weight of said polyesterification condensation product (i) to said nitrodiphenyl ether (ii) in said binder is from about 1:4 to about 4:1.

2. The composition of claim 1 wherein the cellulose acetate analyzes from 54% to 56% by weight of acetic acid.

3. The composition of claim 1 wherein the combustion catalyst is insoluble Prussian blue.

18 9. The composition as described in claim 1 containing from about 1% to about 4% by weight of said composition, an aliphatic oxime corresponding to the empirical formula:

Elf NOH wherein R and R are selected from the class consisting of methyl, ethyl and hydrogen, X is selected from the class consisting of oxygen and NOH, and y is an integer from 0 to 2.

10. The composition of claim 9 wherein the oxime is acetonylacetone dioxime.

11. The composition of claim 9 wherein the oxime is acetylacetone dioxime.

12. A shaped gas-producing propellant grain composition consisting of (a) about 4.75% by weight of cellulose acetate which analyzes 54% to 56% by Weight of acetic acid, (b) about 8% by weight of 2,4-dinitrodiphenyl ether, (0) about 8% by weight of the anhydrous, liquid polyesterification condensation product of ethylene glycol with diglycolic acid, said condensation product having an average molecular weight Within the range of about 350 to about 600, (d) about 3% by weight of insoluble Prussian blue catalyst, (e) about 2.3% by weight of acetonylacetone dioxime, (f) about 1% to about 5% by weight of activated carbon of particle size to pass through a #325 US. Standard sieve and containing not more than about 5% ash and (g) the remainder essentially all ammonium nitrate.

No references cited. 

1. A COMPOSITION OF MATTER SUITABLE FOR USE AS A GASPRODUCING PROPELLANT CONSISTING ESSENTIALLY OF FROM ABOUT 70% TO ABOUT 85% BY WEIGHT OF AMMONIUM NITRATE, FROM ABOUT 1% TO ABOUT 8% BY WEIGHT OF PRUSSIAN BLUE COMBUSTION CATALYST, FROM ABOUT 0.5% TO ABOUT 7% OF FINELY DIVIDED CARBON CONTAINING NOT MORE THAN ABOUT 5% BY WEIGHT OF ASH AND A PLASTIC BINDER MATERIAL IN AN AMOUNT WITHIN THE RANGE OF FROM ABOUT 10% TO ABOUT 25% BY WEIGHT OF SAID COMPOSITION WHICH BINDER MATERIAL CONSISTS ESSENTIALLY OF (A) FROM ABOUT 18% TO ABOUT 40% BY WEIGHT OF CELLULOSE ACETATE WHICH ANALYZES FROM ABOUT 51% TO ABOUT 57% ACETIC ACID AND (B) FROM ABOUT 60% TO ABOUT 82% BY WEIGHT OF PLASTICIZER COMPONENTS CONSISTING ESSENTIALLY OF: (I) THE LIQUID POLYESTERIFICATION CONDENSATION PRODUCT OBTAINED BY REACTING ONE MOL OF AN ALIPHATIC OXYDICARBOXYLIC ACID CONTAINING 4 TO 6 CARBON ATOMS PER MOLECULE WITH ABOUT 1.08 MOLS TO ABOUT 1.30 MOLS OF AT LEAST ONE DIHYDRIC ALCOHOL SELECTED FROM THE CLASS CONSISTING OF ETHYLENE GLYCOL, PROPYLENE GLYCOL, POLYETHYLENE GLYCOL ETHER, POLYPROPYLENE GLYCOL ETHER AND MIXTURES THEREOF WHICH ETHERS AND MIXTURES THEREOF HAVE AN AVERAGE MOLECULAR WEIGHT NOT MORE THAN ABOUT 200 AND WHICH POLYESTERIFICATION CONDENSATION PRODUCT IS ESSENTIALLY ANHYDROUS AND HAS AN AVERAGE MOLECULAR WEIGHT OF ABOUT 250 TO ABOUT 1000, AND (II) AT LEAST ONE NITRODIPHENYL ETHER CONTAINING FROM ONE TO THREE NITRO GROUPS PER MOLECULE AND SUBSTANTIALLY NOT MORE THAN TWO NITRO GROUPS ON ANY BENZENE NUCLEUS, WHEREIN THE RATIO BY WEIGHT OF SAID POLYESTERIFICATION CONDENSATION PRODUCT (I) TO SAID NITRODIPHENYL ETHER (II) IN SAID BINDER IS FROM ABOUT 1:4 TO ABOUT 4:1. 